Your cat is acting differently. Something seems off, but you can’t quite put your finger on it. They may be eating less or more, sleeping more, hiding when they usually seek attention, or suddenly becoming clingy.
Some of the clearest early signs your cat is sick are changes in appetite, energy, hiding, grooming, and litter box habits. This guide explains how to tell if your cat is sick, what each warning sign can mean, and which sick cat symptoms need a vet urgently rather than a wait-and-see approach.
Because cats are good at masking discomfort, a problem may already be well established by the time it becomes obvious. Noticing small changes early gives your veterinarian the best chance to find the cause and treat it. This article is general information, not a diagnosis: if you are worried about your cat, contact your veterinarian.
Table of Contents
Why Cats Hide Illness
Cats are both predators and potential prey, and showing weakness is thought to have made their ancestors more vulnerable. Pet cats still tend to hide signs of pain and illness, so they may look fairly normal until a condition is quite advanced (Cat Friendly Homes).
That is why knowing what is normal for your own cat matters so much. When you know their usual appetite, drinking, litter box output, sleeping spots, and daily routine, even small changes stand out as early warning signs (Cat Friendly Homes).
15 Warning Signs Your Cat Is Sick
1. Changes in Appetite
Appetite changes are often one of the earliest signs. A sick cat may eat less, stop eating entirely, or eat more and still lose weight. Cats should not go without food for long: a cat that stops eating can develop serious complications, including a liver condition called hepatic lipidosis, so a cat that has eaten little or nothing for about a day needs veterinary advice. Our guide to why a cat stops eating covers the common causes.
| Appetite Change | Possible Causes | What to Do |
|---|---|---|
| Eating less | Dental disease, nausea, pain, stress | Book a vet visit within a few days; sooner if other signs appear |
| Not eating at all | Many illnesses, including blockages and organ disease | Contact your vet the same day |
| Eating more but losing weight | Hyperthyroidism, diabetes, intestinal disease, parasites | Book a vet visit within a few days |
| Sudden picky eating, dropping food, chewing on one side | Dental pain, nausea, stress | Book a vet visit; don’t assume it’s fussiness |
2. Changes in Water Intake
Drinking noticeably more or less than usual is worth investigating. Increased thirst, called polydipsia, is often accompanied by more urination and can be linked to kidney disease, diabetes, hyperthyroidism, or liver disease. Drinking less can occur with nausea or general illness and may lead to dehydration. Cats on dry food usually drink more than cats on wet food, so compare against your own cat’s normal rather than an average.
3. Weight Changes
Both weight loss and weight gain matter. Unexplained weight loss is especially concerning and can be associated with kidney disease, hyperthyroidism, diabetes, dental problems, intestinal disease, parasites, or cancer (see our Cat Cancer Complete Guide). Slow weight loss is easy to miss under a fluffy coat, so check your cat’s body regularly: you should be able to feel the ribs under a thin layer of fat without pressing hard. Our body condition score calculator can help you assess this.
Excess weight is also a health issue. Overweight cats are more likely to develop diabetes, arthritis, heart disease, and lower urinary tract disease (Cat Friendly Homes). Learn more about heart-related illness in our Cat Heart Disease Complete Guide.
4. Lethargy
Lethargy is one of the most common signs of illness. Healthy adult cats sleep a lot, but a napping cat should still be alert and responsive when something interesting happens. A sick cat may sleep more, move less, stop playing, or respond less to people and other pets. Lethargy can accompany anything from a mild infection to a serious illness, so a noticeable drop in energy, especially alongside other signs, should be checked by your vet.
5. Hiding
Cats tend to withdraw rather than complain when they don’t feel well. If your normally social cat starts spending time under beds, in closets, or in unusual places, take note. Hiding can be a response to pain or illness, but it can also be caused by fear or stress, for example after a house move or a new pet (see our guide to cat anxiety). Sudden or prolonged hiding, or hiding combined with not eating, should be checked by a vet.
6. Changes in Grooming
Grooming changes can go in either direction. Some cats lick one area excessively, which can point to pain, skin disease, parasites, or stress. Others groom less, leaving a greasy, unkempt, or matted coat, which can be linked to pain (for example arthritis or dental pain), obesity, or general illness. A sudden change in your cat’s usual grooming habits is worth discussing with your vet.
7. Litter Box Changes
Litter box habits tell you a lot. Watch for changes in frequency, amount, appearance, and behavior:
- Straining to urinate with little or no urine. This can mean a urinary blockage, which is a life-threatening emergency, especially in male cats. Go to a vet immediately. Learn the warning signs in our Cat Urinary Blockage Complete Guide.
- Urinating more often or in larger amounts. Possible causes include diabetes, kidney disease, hyperthyroidism, or urinary tract problems. Book a vet visit.
- Blood in the urine or frequent small trips. Often caused by bladder inflammation, stones, or infection. Contact your vet promptly, and treat it as an emergency if your cat is straining or passing little urine.
- Urinating or defecating outside the box. This can reflect a medical problem, pain that makes the box hard to use, stress, or a litter box issue. See our guide to cats peeing outside the litter box.
- Diarrhea. Possible causes include diet changes, intestinal parasites, infections, and inflammatory bowel disease. See our cat diarrhea guide for when to worry.
- Constipation. Small, hard, or infrequent stools can be linked to dehydration, pain, or other illness. Repeated straining without producing stool needs a vet, partly because it can be confused with urinary straining.
- Blood in the stool or black, tarry stool. Contact your vet. Large amounts of blood, black stool, or blood with lethargy or vomiting need urgent care.
8. Vomiting
Vomiting is common in cats, but that doesn’t make it normal. Regular vomiting, including frequent hairballs, can be linked to overgrooming, food sensitivities, inflammatory bowel disease, kidney disease, hyperthyroidism, parasites, or cancer. Keep a note of how often it happens and what comes up. Repeated vomiting in one day, vomiting with blood, or vomiting with lethargy or not eating needs prompt veterinary care. Vomiting with reduced appetite or abdominal discomfort can also be a sign of pancreatitis (see our Cat Pancreatitis Complete Guide), and our cat vomiting guide explains more causes.
9. Breathing Changes
Breathing problems can become serious quickly. Labored or open-mouth breathing needs immediate veterinary attention (International Cat Care), as do rapid breathing at rest, breathing with obvious effort from the belly, or pale or bluish gums. Unlike dogs, cats rarely pant, so panting after only mild activity is a warning sign. Possible causes include asthma, heart disease, pneumonia, fluid around the lungs, and cancer. Coughing or wheezing without distress still needs a prompt vet visit; our Cat Respiratory Infection Complete Guide covers common upper respiratory signs such as sneezing and nasal discharge.
10. Eye Changes
Watch for discharge, redness, cloudiness, unequal pupil sizes, squinting, or a visible third eyelid. These can be caused by infections (including feline herpesvirus), injuries, ulcers, glaucoma, or general illness. Sudden blindness or dilated pupils that don’t respond to light can occur with high blood pressure, which is more common in older cats. Eye problems can worsen quickly, so a painful, squinting, or cloudy eye needs to be seen promptly.
11. Ear Changes
Healthy ears are usually clean and pale pink inside. Watch for dark or waxy discharge, redness, odor, frequent scratching, or head shaking. These can indicate ear mites, yeast or bacterial infection, allergies, or polyps. A head tilt or loss of balance needs prompt attention. Ear problems are often uncomfortable, so have your vet examine them rather than cleaning deep into the ear yourself.
12. Bad Breath
Mild breath odor can be normal, but strong or foul breath is not. The most common cause is dental disease, but bad breath can also be associated with mouth infections, oral tumors, kidney disease, or diabetes. Drooling, pawing at the mouth, dropping food, or red gums alongside bad breath suggest mouth pain. Bad breath is a symptom, not a diagnosis, so ask your vet to examine your cat’s mouth.
13. Behavior Changes
Cats are creatures of habit, so changes in routine are meaningful. New irritability or aggression, withdrawal, unusual clinginess, restlessness, increased vocalizing, confusion, or getting lost in familiar places can all have medical causes such as pain, hyperthyroidism, high blood pressure, or age-related cognitive changes. Stress can cause similar changes, which is another reason to let your vet rule out illness first.
14. Pain Signs
Cats hide pain, and it often shows as a reduction in normal behavior rather than crying out. Signs include grooming, jumping, climbing, playing, or scratching less; hiding; a stiff gait or hesitating before jumping; avoiding being touched; growling or hissing when approached; eating less; and house soiling (International Cat Care). A hunched posture, squinting, and flattened ears can also indicate pain. Untreated pain affects a cat’s welfare, so contact your vet if you suspect it. The Feline Grimace Scale can help you describe what you see. For joint pain in particular, see our cat arthritis guide.
15. Vomiting and Diarrhea Together
Vomiting and diarrhea together can cause dehydration quickly, especially in kittens, senior cats, and cats with existing health problems. Possible causes include dietary upsets, infections, parasites, toxins, swallowed objects, and organ disease. Contact your vet the same day, and seek urgent care if your cat is weak, won’t eat or drink, has blood in the vomit or stool, or may have eaten something toxic.
When to Take Your Cat to the Vet
Any change from your cat’s normal behavior or condition is a reason to talk to your veterinarian (Cat Friendly Homes). The table below is a general guide to how quickly to act. If you are unsure, call your vet or an emergency clinic; they can help you decide.
| How Urgent | Examples |
|---|---|
| Emergency: go now | Labored, open-mouth, or very rapid breathing; straining to urinate with little or no urine; collapse, seizures, or sudden inability to use the back legs; pale or bluish gums; suspected poisoning; injuries such as a fall or road accident; repeated vomiting or vomiting with blood |
| Same day | Not eating for about a day; vomiting and diarrhea together; blood in the urine or stool; marked lethargy or hiding with not eating; a painful, squinting, or cloudy eye; limping or obvious pain |
| Within a few days | Gradual weight loss or gain; drinking or urinating more; reduced grooming or a poor coat; bad breath; mild ear problems; new lumps; subtle behavior changes |
Senior Cat Warning Signs
Cats are generally considered senior from about 11 years of age, and older cats are more likely to develop conditions such as arthritis, chronic kidney disease, hyperthyroidism, diabetes, dental disease, high blood pressure, and cognitive dysfunction. Signs to watch for include drinking and urinating more, weight or muscle loss, a poorer coat, stiffness or reluctance to jump, increased vocalizing, confusion, and changes in sleep patterns. These are not just “old age” and are often treatable or manageable.
The Feline Veterinary Medical Association recommends checkups at least every six months for cats aged 10 to 15 years, and every four months for cats over 15 (Cat Friendly Homes). Our cat life stage calculator can help you see which stage your cat is in.
How to Monitor Your Cat’s Health
- Do a regular body check. Gently feel your cat’s body for lumps, bumps, or tender areas, and look at the eyes, ears, nose, mouth, and coat.
- Monitor weight. Weigh your cat regularly, for example monthly, and keep a record. Our cat weight calculator can help you interpret the numbers. Unexplained weight loss is a red flag.
- Track eating habits. Measure meals and note treats so you know how much your cat normally eats.
- Watch water intake. Notice how quickly bowls or fountains empty, or use our water intake calculator for a rough guide. A clear increase or decrease both matter.
- Check the litter box daily. Note the number and size of urine clumps and the frequency and appearance of stools.
- Note behavior changes. Keep an eye on sleep patterns, favorite resting spots, activity, and social behavior.
- Keep health records. Record vaccinations, medications, past illnesses, and any changes you notice, with dates. Short videos of unusual behavior can also help your vet.
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Get the Bundle →Key Takeaways
You are often the first person to notice that something is wrong with your cat. If something seems off, trust that observation and talk to your vet rather than waiting for the problem to become obvious.
- Know your cat’s baseline. Normal weight, appetite, drinking, litter box habits, and behavior make changes easier to spot.
- Small changes matter. A slight drop in appetite, gradual weight loss, or a subtle behavior shift can be an early sign.
- Cats hide illness. Regular checkups help catch problems you can’t see at home.
- Don’t self-diagnose. The same sign can have many causes, so let your vet examine your cat before you try home treatments.
- Know the emergency signs. Breathing difficulty, straining to urinate with little or no urine, collapse, seizures, and suspected poisoning need immediate care.
- Senior cats need more frequent checkups. At least every six months from about age 10, and more often for cats over 15.
- Keep records. Notes on weight, eating, behavior, and medications help your vet reach a diagnosis.
FAQ
How do I know if my cat is sick?
Look for changes from your cat’s normal: appetite, water intake, weight, energy, grooming, litter box habits, and behavior. Because cats hide illness, even subtle changes matter. If you notice a change and aren’t sure what it means, contact your vet.
What are the signs of a sick cat?
Common sick cat symptoms include loss of appetite, lethargy, hiding, weight loss, vomiting, diarrhea, drinking or urinating more, breathing changes, litter box changes, poor grooming, and behavior changes. Several signs together usually make the situation more urgent.
When should I take my cat to the vet?
Go immediately for breathing difficulty, straining to urinate with little or no urine, collapse, seizures, or suspected poisoning. Contact your vet the same day if your cat hasn’t eaten for about a day, has vomiting and diarrhea together, or has blood in the urine or stool. Book an appointment for gradual changes such as weight loss or increased thirst. When in doubt, call your vet.
Why is my cat hiding and not eating?
Hiding combined with not eating is a common sign that a cat feels unwell. Possible causes include pain, nausea, infection, dental disease, organ disease, and severe stress. This combination needs prompt veterinary attention, ideally the same day.
Can I tell if my cat has a fever at home?
Not reliably by touch. Warm ears or a dry nose don’t confirm a fever. A cat’s normal rectal temperature is about 100.5–102.5°F (38.1–39.2°C) (Merck Veterinary Manual), and a rectal reading is the most accurate method. Ear thermometers can be less reliable. Taking a temperature can stress or injure a cat, so ask your vet to show you how, or have your vet check it if your cat seems unwell.
Why is my cat sleeping more than usual?
Healthy adult cats sleep a lot, so look for a change from their normal pattern. Sleeping much more, being hard to rouse, or showing little interest when awake can be linked to pain, infection, anemia, organ disease, or other illness. See your vet, especially if there are other symptoms.
How can I tell if my cat is in pain?
Pain often shows as doing less: less grooming, jumping, playing, or interacting. Other signs include hiding, a hunched posture, squinting, a stiff gait, reacting when touched, eating less, and toileting outside the box. Contact your vet if you suspect pain.
What does it mean when a cat stops grooming?
Reduced grooming often points to an underlying problem such as pain (for example arthritis or dental disease), obesity, or general illness. A greasy, matted, or unkempt coat in a cat that used to groom well needs a veterinary check.
Why is my cat drinking more water than usual?
Increased thirst can be associated with kidney disease, diabetes, hyperthyroidism, liver disease, or urinary problems. A change of diet from wet to dry food can also increase drinking. If your cat is clearly drinking more without an obvious reason, see your vet. Blood and urine tests can usually identify the cause.
Is my cat sick or just old?
Some changes come with age, but weight loss, increased thirst, stiffness, confusion, and behavior changes are not just “getting old.” They often have treatable causes. Senior cats benefit from checkups at least every six months so problems are found early.
Can cats hide illness for a long time?
Yes. Signs of chronic conditions such as kidney disease or arthritis can be subtle for weeks or months. Knowing your cat’s normal routine and keeping up with regular checkups helps catch problems that are easy to miss at home.
What are emergency signs in cats?
Emergency signs include labored or open-mouth breathing, straining to urinate with little or no urine, collapse, seizures, sudden inability to use the back legs, pale or bluish gums, suspected poisoning, injuries, and repeated vomiting or vomiting blood. Go to a vet or emergency clinic immediately.
Sources & References
- Cat Friendly Homes (Feline Veterinary Medical Association) — Signs & Symptoms — https://catfriendly.com/signs-symptoms/
- Cat Friendly Homes (Feline Veterinary Medical Association) — What Is Normal? — https://catfriendly.com/keep-your-cat-healthy/what-is-normal/
- Cat Friendly Homes (Feline Veterinary Medical Association) — Senior Care — https://catfriendly.com/life-stages/senior-care/
- International Cat Care — How to Spot Signs of Pain in Cats — https://icatcare.org/news/how-to-spot-signs-of-pain-in-cats-pain-awareness-month-2026
- International Cat Care — Physical Health — https://icatcare.org/articles/physical-health
- Merck Veterinary Manual — Normal Rectal Temperature Ranges — https://www.merckvetmanual.com/multimedia/table/normal-rectal-temperature-ranges
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